Have you ever installed an original refurbished iPhone 7, 7+, 8 or 8+ screen into your customer’s phone only to find that the touch isn’t working? Or perhaps the touch was okay when you checked it, but your customer still comes back the next day saying it has stopped working? It’s easy to blame this problem on a faulty screen, but it may not be as simple as that.
Different Manufacturers- Different Calibration Settings
There are three companies who make screens for the iPhone; LG, Toshiba, and Sharp. Although the LCDs themselves are made to Apple’s strict specification, compatibility between iPhone devices varies greatly. If you look at the 3D touch panel, there is a long serial code which might not look like it means anything but can be decoded to the following. The first three letters identify the maker of the LCD and 3D touch panel and the remaining digits are the serial- unique to that LCD. This information is also contained in the QR code on the back of the screen and is recorded in Apple’s GSX server against the IMEI and the serial number of the device. This is one of the ways Apple can tell if the iPhone has ever had the screen changed.
Toshiba LCDs start with C11 or F7C
LG LCDs start with DTP or C3F
Sharp LCDs start with DKH or C0N
It would be fair to say that if Toshiba manufactured the LCD they would also manufacture the 3D touch panel that is attached to the LCD. This would be the same for LG and Sharp. When the iPhone is made in the factory and the first screen is installed, Apple uses a special calibration machine to calibrate the iPhone to work with the screen. We believe a similar machine is used if you ever take an iPhone direct to Apple for a screen replacement. At this point, it doesn’t matter whether the iPhone gets an LG, Toshiba or Sharp LCD as the calibration machine will make sure it is configured correctly. Sometimes the calibrated screen has touch issue, too.
If the iPhone was calibrated for a Toshiba or Sharp screen and you cross install between these 2 manufacturers there is roughly a 5% chance of bad touch. If the iPhone was originally calibrated for an LG screen and you cross install with a Toshiba or Sharp screen then there is a 50% chance of touch problems because LG’s sensitivity range distribution is very different to these 2 manufacturers. Without having the magic calibration box to tell the iPhone you’ve installed a different manufacturer’s screen you are going to have trouble unless you install an LG screen. This probably explains why, if you install a screen and experience touch problems, then install another screen and it works, you’d automatically assume a bad screen. However, it is possible you’ve just switched manufacturer and got lucky. If you used the suspected bad screen in the next repair it would more than likely work with no issues.